1. Field of the Invention
The present invention relates to a procedure for the self-adapting processing of digital signals and its application to a multiplexed self-adapting echo canceler, especially for passing through digital telephone exchanges and for long-distance telephone connections.
2. Description of the Prior Art
When a 4-wire circuit in a telephone transmission channel is connected to a 2-wire circuit, the change from the 4-wire mode to the 2-wire mode is made by means of a terminator. This terminator is a hybrid network or a bridge circuit, with or without a transformer, which in practice results in rather approximate separation between the outgoing and incoming signals.
The elimination of signals reflected by the 4-wire/2-wire terminator by means of an adaptive echo canceler is satisfactory, but echo cancelers operating in accordance with presently known digital signal processing procedures are very costly and voluminous, especially if they are multiplexed.
The purpose of the present invention is to propose a new digital signal processing procedure allowing the shared-time processing over a large number of channels in a dependable manner.
The present invention also relates to a digital filter, in particular an echo canceler for embodiment of the said procedure, this echo canceler producing practically zero attenuation of signals passing through 2-wire digital telephone exchanges and almost completely eliminating echo when used for long-distance telephone connections, this echo canceler having the least possible size and the lowest possible cost.